I. Field of the Invention
The present invention relates to the field of boilers for hot water heating systems, and more particularly the present invention relates to the field of waste heat recovery from boiler flue gases. Even more particularly the present invention relates to the field of waste heat extraction from boiler flue gases to warm the incoming flow of water into the boiler.
II. Prior Art Statement
A search of the issued United States patents reveals the following United States patents which have been issued in the field relating to the present invention. U.S. Pat. No. 576,718 discloses a system for circulating room air across the condensing coil of a steam engine to condense the steam and warm the room air. U.S. Pat. No. 1,028,030 discloses a coke making plant wherein waste gas from the coke production is utilized to produce steam for operating a steam engine. U.S. Pat. No. 2,026,399 discloses a system for utilizing flue gas heat to heat hot water for household use. U.S. Pat. No. 2,072,427 discloses an air conditioning system wherein room air is blown past cold liquid conduits to cool the room air and prevent condensation on the conduits. U.S. Pat. No. 1,214,255 discloses a system which utilizes the waste heat of a refrigeration system to augment a dwelling heating system. U.S. Pat. No. 2,166,355 discloses a system for utilizing flue gas waste heat to heat water in a hot water tank for household use. U.S. Pat. No. 3,473,603 discloses an air to liquid heat exchanger which employs a coil and fins to improve heat transfer from the air to the liquid. U.S. Pat. No. 3,896,922 discloses a plurality of pipes including heat recovery pipes in heat exchange relationships with the hot flue gases in the flue of a furnace to heat water for space heaters and to pre-heat water for household use. U.S. Pat. No. 4,109,858 discloses a system which utilizes heat exchangers in a room having excess heat to warm water for household purposes.
In the March 1979 issue of "Popular Science" on Page 70 an article by Louis Caso discloses a system for extracting waste heat from a boiler flue gas to heat water in a storage tank. The storage tank is employed to provide warm water to a circulating pump inlet. A heat exchanger is placed in the boiler flue and a thermo syphon method is employed to circulate cold water from the storage tank bottom through the heat exchanger where the water is heated and returned to the top of the storage tank. The flow of water through the heat exchanger is soley induced by the thermo syphon method and no provision is made for selective circulation of water through the heat exchanger.
None of the above listed United States patents, nor the magazine article, disclose a flue gas heat recovery system for dwelling hot water heating system boilers which utilizes a heat exchanger in the flue for extracting heat from the combustion products of the boiler to warm water from room radiators before the water is returned to the boiler. None of the above listed United States patents disclose a system for controlling the amount of water circulating through the heat exchanger by means of a by-pass conduit and control valves.